<%@ page contentType="image/jpeg" import="java.awt.*,java.util.*,java.awt.image.*,javax.imageio.*" pageEncoding="UTF-8" %>
<%!
Color getRandColor(int fc,int bc){//给定范围获得随机颜色
  Random random = new Random();
  	if(fc>255) fc=255;
  	if(bc>255) bc=255;
  	int r=fc+random.nextInt(bc-fc);
  	int g=fc+random.nextInt(bc-fc);
  	int b=fc+random.nextInt(bc-fc);
  		return new Color(r,g,b);
  }
%>
<%
//设置页面不缓存
response.reset();
response.setHeader("Pragma","No-cache");
response.setHeader("Cache-Control","no-cache");
response.setDateHeader("Expires", 0);

// 在内存中创建图象
int width=104, height=34;
BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);

// 获取图形上下文
Graphics g = image.getGraphics();

//生成随机类
Random random = new Random();

// 设定背景色
g.setColor(new Color(241,244,245));
g.drawRect(0, 0, width, height);
g.setColor(new Color(241,244,245));
g.fillRect(0, 0, width, height);
//设定字体


// 随机产生155条干扰线，使图象中的认证码不易被其它程序探测到


// 取随机产生的认证码(4位数字)

g.setFont(new Font("微软雅黑",Font.BOLD,20));
String codeList = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz1234567890";

StringBuffer sRand= new StringBuffer("");


for (int i=0;i<4;i++){
	  int a=random.nextInt(codeList.length()-1);
	  String rand=codeList.substring(a,a+1);
	  sRand.append(rand);
	  // 将认证码显示到图象中
	  g.setColor(new Color(80,201,64));//调用函数出来的颜色相同，可能是因为种子太接近，所以只能直接生成
	  //g.translate(random.nextInt(3), random.nextInt(3));
	  g.drawString(rand,23*i+6,26);
}

// 将认证码存入SESSION
session.removeAttribute("code");
session.setAttribute("code",sRand.toString());
// 图象生效
g.dispose();

// 输出图象到页面

ImageIO.write(image, "JPEG", response.getOutputStream());
out.clearBuffer();
out = pageContext.pushBody();


%>

